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BackgroundThe pipeline embolization device (PED; Medtronic) has presented as a safe and efficacious treatment for small- and medium-sized intracranial aneurysms. Independently adjudicated long-term results of the device in treating these lesions are still indeterminate. We present 3-year results, with additional application of a flow diverter specific occlusion scale.MethodsPREMIER (prospective study on embolization of intracranial aneurysms with pipeline embolization device) is a prospective, single-arm trial. Inclusion criteria were patients with unruptured wide-necked intracranial aneurysms ≤12 mm. Primary effectiveness (complete aneurysm occlusion) and safety (major neurologic event) endpoints were independently monitored and adjudicated.ResultsAs per the protocol, of 141 patients treated with a PED, 25 (17.7%) required angiographic follow-up after the first year due to incomplete aneurysm occlusion. According to the Core Radiology Laboratory review, three (12%) of these patients progressed to complete occlusion, with an overall rate of complete aneurysm occlusion at 3 years of 83.3% (115/138). Further angiographic evaluation using the modified Cekirge–Saatci classification demonstrated that complete occlusion, neck residual, or aneurysm size reduction occurred in 97.1%. The overall combined safety endpoint at 3 years was 2.8% (4/141), with only one non-debilitating major event occurring after the first year. There was one case of aneurysm recurrence but no cases of delayed rupture in this series.ConclusionsThe PED device presents as a safe and effective modality in treating small- and medium-sized intracranial aneurysms. The application of a flow diverter specific occlusion classification attested the long-term durability with higher rate of successful aneurysm occlusion and no documented aneurysm rupture.Trial registrationNCT02186561.

Background The development of flow-diverters such as the Pipeline embolization device (PED) have allowed for safe and effective treatment of challenging and/or previously untreatable intracranial aneurysms. A rare but serious complication during PED deployment involves fracture of single or multiple components, which can lead to retained hardware. To date, there are little data regarding the safety of performing magnetic resonance imaging (MRI) when tip or capture coils remain intracranially. Case Description To the best of our knowledge, we present the first case demonstrating the safe completion of MRI after treatment of 2 posterior circulation aneurysms in a woman aged 69 years presenting with subarachnoid hemorrhage whose treatment was complicated by fracture and subsequent retention of the PED tip and capture coils. Conclusions MRI (1.5T) appears safe and effective in patients who have retained PED tips and/or capture coils.

BackgroundPreliminary clinical studies on the safety and efficacy of the pipeline embolization device (PED) for the treatment of small/medium aneurysms have demonstrated high occlusion rates with low complications.ObjectiveTo evaluate the safety and effectiveness of the PED for treatment of wide necked small and medium intracranial aneurysms.MethodsPREMIER is a prospective, multicenter, single arm trial. Patients were treated with the PED for unruptured wide necked aneurysms, measuring ≤12 mm along the internal carotid artery or vertebral artery, between July 2014 and November 2015. At 1 year post-procedure, the primary effectiveness endpoint was complete occlusion (Raymond grade 1) without major parent vessel stenosis (≤50%) or retreatment, and the primary safety endpoint was major stroke in the territory supplied by the treated artery or neurologic death.ResultsA total of 141 patients were treated with PEDs (mean age 54.6±11.3 years, 87.9% (124/141) women). Mean aneurysm size was 5.0±1.92 mm, and 84.4% (119/141) measured ConclusionsTreatment of wide necked small/medium aneurysms with the PED results in high rates of complete occlusion without significant parent vessel stenosis and low rates of permanent neurologic complications.Trial registrationNCT02186561.

Background and Purpose— Mechanical thrombectomy has been shown to improve clinical outcomes in patients with acute ischemic stroke. However, the impact of balloon guide catheter (BGC) use is not well established. Methods— STRATIS (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke) was a prospective, multicenter study of patients with large vessel occlusion treated with the Solitaire stent retriever as first-line therapy. In this study, an independent core laboratory, blinded to the clinical outcomes, reviewed all procedures and angiographic data to classify procedural technique, target clot location, recanalization after each pass, and determine the number of stent retriever passes. The primary clinical end point was functional independence (modified Rankin Scale, 0–2) at 3 months as determined on-site, and the angiographic end point was first-pass effect (FPE) success rate from a single device attempt (modified Thrombolysis in Cerebral Infarction, ≥2c) as determined by a core laboratory. Achieving modified FPE (modified Thrombolysis in Cerebral Infarction, ≥2b) was also assessed. Comparisons of clinical outcomes were made between groups and adjusted for baseline and procedural characteristics. All participating centers received institutional review board approval from their respective institutions. Results— Adjunctive technique groups included BGC (n=445), distal access catheter (n=238), and conventional guide catheter (n=62). The BGC group had a higher rate of FPE following first pass (212/443 [48%]) versus conventional guide catheter (16/62 [26%]; P =0.001) and distal access catheter (83/235 [35%]; P =0.002). Similarly, the BGC group had a higher rate of modified FPE (294/443 [66%]) versus conventional guide catheter (26/62 [42%]; P P =0.003). The BGC group achieved the highest rate of functional independence (253/415 [61%]) versus conventional guide catheter (23/55 [42%]; P =0.007) and distal access catheter (113/218 [52%]; P =0.027). Final revascularization and mortality rates did not differ across the groups. Conclusions— BGC use was an independent predictor of FPE, modified FPE, and functional independence, suggesting that its routine use may improve the rates of early revascularization success and good clinical outcomes. Clinical Trial Registration— URL: https://www.clinicaltrials.gov . Unique identifier: NCT02239640.

Background and Purpose— Although intracranial thrombectomy represents the standard treatment approach for anterior circulation tandem occlusions, whether the extracranial lesion requires acute stenting remains unclear. Our aim was to investigate differences in clinical and procedural outcomes related to stenting extracranial lesions in a registry of patients undergoing thrombectomy for acute stroke. Methods— Data were analyzed from the STRATIS registry (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke)—a prospective, nonrandomized study of patients undergoing neurothrombectomy with the Solitaire device. A total of 984 patients treated at 55 sites were analyzed. Univariate and multivariable logistic regression was used to assess relationship between outcome and procedural technique. Results— Of 147 (14.9%) patients with tandem lesions treated, stenting of the extracranial lesion during thrombectomy was performed in 80 patients and withheld in 67 patients. There were no differences between groups with respect to age, ASPECTS (Alberta Stroke Program Early CT Score), or intravenous-tPA (tissue-type plasminogen activator) use. However, the patients in the stenting group had lower baseline National Institutes of Health Stroke Scale (16 versus 17.9; P =0.07), shorter onset to arterial puncture time (133.6 versus 163.4 minutes; P =0.04), and lower rates of atrial fibrillation (6.3% versus 25.4%) as compared to the nonstenting group. Good outcomes (modified Rankin Scale, 0–2 at 90 days) were higher in the stenting group (68.5% versus 42.2%; P =0.003) with no difference in mortality or symptomatic hemorrhage. After adjustment for covariates, stenting continued to be associated with superior outcomes. Conclusions— Acute stenting of an extracranial carotid stenosis during neurothrombectomy can be achieved with equal safety compared with no stenting. Carotid stenting in the acute phase may lead to better outcomes; this should ideally be confirmed by randomized trials.

Background: Subarachnoid hemorrhage (SAH) associated with vessel injury during endovascular therapy for acute ischemic stroke is a known complication. Arterial anatomy may predispose to increased risk of SAH and technical safety, yet factors such as clot location, arterial size and tortuosity have not been explored. We examined these anatomical factors with respect to SAH during thrombectomy. Methods: Arterial anatomy at the site of occlusion and mechanical thrombectomy during device deployment was detailed by the STRATIS core lab. Luminal diameters, arterial branching and segmental tortuosity were measured. Arterial tortuosity was quantified using the distance factor metric (DFM). Statistical analyses included descriptives of arterial anatomy, with univariate and multivariate modeling to predict SAH. Results: Arterial tortuosity in each segment from the proximal cerebral arteries to the site of occlusion was quantified in 790 subjects treated with mechanical thrombectomy in STRATIS. Cumulative arterial tortuosity to the site of vessel occlusion was greater in distal lesions (Table 1). SAH was clearly linked with more distal thrombectomy (p=0.017), with 19.0% of distal M2, 16.7% of M3, 7.3% of distal M1, 5.8% of proximal M2, 2.4% of distal ICA and 2.1% of proximal M1. Multivariate prediction of SAH revealed that arterial diameter was unrelated to SAH (p=0.30) when accounting for tortuosity, whereas the presence of tortuosity tripled the risk of SAH (OR 3, p Conclusions: This novel systematic analysis of arterial tortuosity and angiographic anatomy during mechanical thrombectomy establishes tortuosity as a determinant of SAH, providing insight for future techniques and innovative device designs.

Background: Mechanical thrombectomy is established for large vessel occlusions in acute ischemic stroke, but the potential role in distal vessel occlusions of medium arteries is largely unknown. Such distal arterial segments have not been measured with respect to thrombectomy devices used during endovascular therapy. We conducted a systematic analysis of arterial size, segmental anatomy and stent retriever device performance during thrombectomy. Methods: The STRATIS angiography core lab adjudicated the exact location of the occlusion, proximal and distal device deployment, relationship to arterial bifurcations and anatomical nomenclature. Arterial diameters were measured at all of these sites. Statistical analyses examined the relationship between these variables, arterial recanalization and eTICI reperfusion. Results: Thrombectomy was performed with various device sizes, including Solitaire 4x40 in 36.3% (306/844), Solitaire 6x30 in 31.4% (265/844), Solitaire 4x20 in 26.4% (223/844), unspecified in 3.8% (32/844), Solitaire 6x20 in 1.3% (11/844) and Solitaire 4x15 in 0.8% (7/844). Arterial diameter at the occlusion site was median 2.17mm (1.40-3.59) in the distal M1, 1.67mm (0.81-2.98) in the proximal M2, 1.50mm (0.92-1.99) in the distal M2, 1.24mm (0.67-2.00) in the M3 and 1.88mm (1.49-1.94) in the P1. Considerable overlap was noted between arterial sizes at occlusion sites carrying different segmental arterial nomenclature or vessel names. During device deployment in STRATIS, median arterial diameter at the occlusion site was 2.4mm (IQR 1.9, 3.4), 2.9mm (IQR 2.2, 3.6) at the proximal stent marker and 1.4mm (IQR 1.2, 1.7) at the distal stent marker. Substantial eTICI reperfusion (2b-3) was achieved in all distal vessel occlusions (Table 1). Conclusions: Substantial reperfusion may be achieved with currently available mechanical thrombectomy devices for distal vessel occlusions in medium arteries.

BACKGROUND The effect of endovascular thrombectomy that is performed more than 6 hours after the onset of ischemic stroke is uncertain. Patients with a clinical deficit that is disproportionately severe relative to the infarct volume may benefit from late thrombectomy. METHODS We enrolled patients with occlusion of the intracranial internal carotid artery or proximal middle cerebral artery who had last been known to be well 6 to 24 hours earlier and who had a mismatch between the severity of the clinical deficit and the infarct volume, with mismatch criteria defined according to age (= 80 years). Patients were randomly assigned to thrombectomy plus standard care (the thrombectomy group) or to standard care alone (the control group). The coprimary end points were the mean score for disability on the utility-weighted modified Rankin scale (which ranges from 0 [death] to 10 [no symptoms or disability]) and the rate of functional independence (a score of 0, 1, or 2 on the modified Rankin scale, which ranges from 0 to 6, with higher scores indicating more severe disability) at 90 days. RESULTS A total of 206 patients were enrolled; 107 were assigned to the thrombectomy group and 99 to the control group. At 31 months, enrollment in the trial was stopped because of the results of a prespecified interim analysis. The mean score on the utility-weighted modified Rankin scale at 90 days was 5.5 in the thrombectomy group as compared with 3.4 in the control group (adjusted difference [Bayesian analysis], 2.0 points; 95% credible interval, 1.1 to 3.0; posterior probability of superiority, >0.999), and the rate of functional independence at 90 days was 49% in the thrombectomy group as compared with 13% in the control group (adjusted difference, 33 percentage points; 95% credible interval, 24 to 44; posterior probability of superiority, >0.999). The rate of symptomatic intracranial hemorrhage did not differ significantly between the two groups (6% in the thrombectomy group and 3% in the control group, P = 0.50), nor did 90-day mortality (19% and 18%, respectively; P = 1.00). CONCLUSIONS Among patients with acute stroke who had last been known to be well 6 to 24 hours earlier and who had a mismatch between clinical deficit and infarct, outcomes for disability at 90 days were better with thrombectomy plus standard care than with standard care alone. (Funded by Stryker Neurovascular; DAWN ClinicalTrials.gov number, NCT02142283.)

Supplemental Digital Content is available in the text., Background: Endovascular treatment with mechanical thrombectomy (MT) is beneficial for patients with acute stroke suffering a large-vessel occlusion, although treatment efficacy is highly time-dependent. We hypothesized that interhospital transfer to endovascular-capable centers would result in treatment delays and worse clinical outcomes compared with direct presentation. Methods: STRATIS (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke) was a prospective, multicenter, observational, single-arm study of real-world MT for acute stroke because of anterior-circulation large-vessel occlusion performed at 55 sites over 2 years, including 1000 patients with severe stroke and treated within 8 hours. Patients underwent MT with or without intravenous tissue plasminogen activator and were admitted to endovascular-capable centers via either interhospital transfer or direct presentation. The primary clinical outcome was functional independence (modified Rankin Score 0–2) at 90 days. We assessed (1) real-world time metrics of stroke care delivery, (2) outcome differences between direct and transfer patients undergoing MT, and (3) the potential impact of local hospital bypass. Results: A total of 984 patients were analyzed. Median onset-to-revascularization time was 202.0 minutes for direct versus 311.5 minutes for transfer patients (P

Background and Purpose— Mechanical thrombectomy with stent retrievers has become standard of care for treatment of acute ischemic stroke patients because of large vessel occlusion. The STRATIS registry (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke) aimed to assess whether similar process timelines, technical, and functional outcomes could be achieved in a large real world cohort as in the randomized trials. Methods— STRATIS was designed to prospectively enroll patients treated in the United States with a Solitaire Revascularization Device and Mindframe Capture Low Profile Revascularization Device within 8 hours from symptom onset. The STRATIS cohort was compared with the interventional cohort of a previously published SEER patient-level meta-analysis. Results— A total of 984 patients treated at 55 sites were analyzed. The mean National Institutes of Health Stroke Scale score was 17.3. Intravenous tissue-type plasminogen activator was administered in 64.0%. The median time from onset to arrival in the enrolling hospital, door to puncture, and puncture to reperfusion were 138, 72, and 36 minutes, respectively. The Core lab–adjudicated modified Thrombolysis in Cerebral Infarction ≥2b was achieved in 87.9% of patients. At 90 days, 56.5% achieved a modified Rankin Scale score of 0 to 2, all-cause mortality was 14.4%, and 1.4% suffered a symptomatic intracranial hemorrhage. The median time from emergency medical services scene arrival to puncture was 152 minutes, and each hour delay in this interval was associated with a 5.5% absolute decline in the likelihood of achieving modified Rankin Scale score 0 to 2. Conclusions— This largest-to-date Solitaire registry documents that the results of the randomized trials can be reproduced in the community. The decrease of clinical benefit over time warrants optimization of the system of care. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT02239640.

OBJECTIVE The primary imaging modalities used to select patients for endovascular thrombectomy (EVT) are noncontrast computed tomography (CT) and CT perfusion (CTP). However, their relative utility is uncertain. We prospectively assessed CT and CTP concordance/discordance and correlated the imaging profiles on both with EVT treatment decisions and clinical outcomes. METHODS A phase 2, multicenter, prospective cohort study of large-vessel occlusions presented up to 24 hours from last known well was conducted. Patients received a unified prespecified imaging evaluation (CT, CT angiography, and CTP with Rapid Processing of Perfusion and Diffusion software mismatch determination). The treatment decision, EVT versus medical management, was nonrandomized and at the treating physicians' discretion. An independent, blinded, neuroimaging core laboratory adjudicated favorable profiles based on predefined criteria (CT:Alberta Stroke Program Early CT Score ≥ 6, CTP:regional cerebral blood flow (

Background: Different neuroimaging triage strategies, including CT perfusion (CTP), are commonly used prior to endovascular therapy, often tailoring imaging approaches based on time from symptom onset. We analyzed whether the acquisition of CTP prior to endovascular therapy in STRATIS was related to clinical outcomes and if any possible link was noted based on time duration from symptom onset. Methods: The STRATIS Core Lab analyzed all pre-procedural imaging in STRATIS, including the use of CTP. Acquisition of pre-procedural CTP was analyzed with respect to 90-day modified Rankin Score (mRS) clinical outcomes. Subgroup analyses explored whether this relationship was different in the 0-6 versus 6-8 hour interval from symptom onset. Results: Among 984 subjects analyzed in STRATIS, 264 had pre-procedural CTP acquired by the imaging Core Laboratory. No association between CTP acquisition and mRS outcomes at 90 days was observed in the overall study cohort. However, among subjects treated over 6 hours from onset (n=119), a trend toward better outcomes was observed in those with CTP acquisition compared to those without (adjusted common odds ratio 1.86, p=0.092). This association was not present in subjects treated within 6 hours from onset (adjusted common odds ratio 1.10, p=0.498) (Figure). Conclusions: Real-world data from STRATIS reveal that good clinical outcomes after endovascular therapy are not directly contingent on obtaining pre-procedural CTP. Subgroup analyses provide novel data that CTP may not be necessary 0-6 hours from onset, yet CTP may be linked with better outcomes in patients presenting after 6 hours.

Introduction: Interhospital transfer for endovascular treatment of large vessel occlusion (LVO) stroke results in significant delays and worse outcomes. We hypothesized that interhospital patient transfer using air transport would result in shorter transit times compared to ground ambulance. Methods: Subjects from the STRATIS registry that underwent interhospital transfer for endovascular treatment were separated by air transport vs. ground ambulance transport and analyzed by transfer distance. The primary endpoint was transfer-time, calculated as the time from imaging at the initial hospital to arrival at the treating hospital. Also assessed was travel-time, calculated as time of departure from the initial hospital to arrival at the treating hospital. Results: There were 232 subjects from 41 sites. Mean transfer-time for all air subjects (n=118) was 147.1 min, and for all ground subjects (n=114) was 130.0 min (p=0.019). Mean travel-time was 45.0 min for air transport and 40.2 min for ground transport (p=0.239); though the average travel distance was longer for air (65.5 miles) vs. ground (27.6 miles; p Conclusions: In this large, real-world study, interhospital transfer via air transport did not result in faster transfer times compared to ground ambulance. In fact, there was an advantage to ground transportation for distances of less than 20 miles. These results suggest that ground ambulance should routinely be used for interhospital transfer of stroke patients for travel less than 20 miles.

Background: Collateral grade is an established determinant of outcomes in acute ischemic stroke (AIS). The triage, workflow and therapeutic options for AIS may be tailored to collaterals and identifying key predictors of collateral status may therefore be crucial. We hypothesized that degree of collateral circulation prior to endovascular therapy in AIS may be predicted at the time of initial patient evaluation and triage. Methods: The STRATIS Registry showed that timelines, technical, and functional outcomes could be effectively attained in a large real-world cohort of endovascular therapy. Baseline clinical and imaging predictors of core lab adjudicated collateral grade (ASITN) by conventional angiography were determined, using multivariate modeling. Results: 586 STRATIS subjects (67.5 ± 15.2 years, 52.7% male) presenting with AIS at 147.4 ± 101.8 min from symptom onset (TFSO) and median NIHSS score 17.0 (range 8.0,30.0) were analyzed. Collateral grade was poor (ASITN 0-1) in 81, moderate (ASITN 2) in 297 and good (ASITN 3-4) in 208. Baseline stroke severity inversely correlated with collaterals (NIHSS per point, OR 0.946, 0.916-0.977, p=0.001), yet no clinical variables such as age, sex or co-morbidities were predictive of collateral status. Less severe ASPECTS at imaging triage (median 9, range 2-10) was associated with better collateral grade (ASITN 0-1, median 7 (2-10); ASITN 2, 8 (3-10); ASITN 3-4, 9 (5-10), p Conclusions: Imaging, using only ASPECTS, during triage strongly predicts collateral grade, irrespective of time from symptom onset. Clinical variables, however, may not be used to accurately predict collaterals in the real-world practice of endovascular therapy.

Background and Purpose- Although intracranial thrombectomy represents the standard treatment approach for anterior circulation tandem occlusions, whether the extracranial lesion requires acute stenting remains unclear. Our aim was to investigate differences in clinical and procedural outcomes related to stenting extracranial lesions in a registry of patients undergoing thrombectomy for acute stroke. Methods- Data were analyzed from the STRATIS registry (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke)-a prospective, nonrandomized study of patients undergoing neurothrombectomy with the Solitaire device. A total of 984 patients treated at 55 sites were analyzed. Univariate and multivariable logistic regression was used to assess relationship between outcome and procedural technique. Results- Of 147 (14.9%) patients with tandem lesions treated, stenting of the extracranial lesion during thrombectomy was performed in 80 patients and withheld in 67 patients. There were no differences between groups with respect to age, ASPECTS (Alberta Stroke Program Early CT Score), or intravenous-tPA (tissue-type plasminogen activator) use. However, the patients in the stenting group had lower baseline National Institutes of Health Stroke Scale (16 versus 17.9; P=0.07), shorter onset to arterial puncture time (133.6 versus 163.4 minutes; P=0.04), and lower rates of atrial fibrillation (6.3% versus 25.4%) as compared to the nonstenting group. Good outcomes (modified Rankin Scale, 0-2 at 90 days) were higher in the stenting group (68.5% versus 42.2%; P=0.003) with no difference in mortality or symptomatic hemorrhage. After adjustment for covariates, stenting continued to be associated with superior outcomes. Conclusions- Acute stenting of an extracranial carotid stenosis during neurothrombectomy can be achieved with equal safety compared with no stenting. Carotid stenting in the acute phase may lead to better outcomes; this should ideally be confirmed by randomized trials.

Objective The purpose of this study is to compare the outcomes of percutaneous transluminal angioplasty and stenting (PTAS) for intracranial arterial stenosis (ICAS) using self-expanding (SE) stents, bare metal balloon expandable (BMBE) stents, and (anti-mitogenic) drug-eluting balloon expandable (DEBE) stents. Methods We retrospectively reviewed all 195 cases of intracranial stenting for atherosclerotic stenosis performed by a single operator at a single institution from August 1998 to August 2017. Rates of residual stenosis, in-stent restenosis (ISRS) and adverse events were calculated for patients treated with each stent type. Results The results of the analysis for the entire cohort will be presented. Currently we report the results of our analysis for 60 patients for whom all desired data points were available. Mean pre-procedural stenosis rate was 84%. Of these, 42 were treated with SE (Wingspan) stents and 18 were treated with DEBE stents. The mean angiographic follow-up period was 8.2±4.5 months. The rate of significant residual stenosis immediately after PTAS (≥30%) was higher in the SE group (42.5%, 17 of 40) than the DEBE group (11.1%, 2 of 18; p=0.02). The rate of significant in-stent restenosis (≥50%) at angiographic follow-up was also higher in the SE group (47.5%, 19 of 40) than the DEBE group (16.6%, 3 of 18; p=0.03). The incidence of an ischemic event in the same distribution as the stent was higher in the SE group (37.5%, 15 of 40) than the DEBE group (11.1%, 2 of 18; p=0.039). The incidence of stroke or death within 30 days of PTAS was higher in the SE group (7.1%, 2 of 42 died from ICH, 1 of 42 from ischemic stroke) than the DEBE group (0%, 0 of 18; p=0.25). The incidence of TIA, stroke, or death within 30 days of PTAS was also higher in the SE group (9.5%, 4 of 42) than the DEBE group (0%, 0 of 18; p=0.18). Conclusion In regards to post-operative residual stenosis, in-stent restenosis, periprocedural complications, and ischemic events within the same distribution as the affected artery, DEBE stents were more effective than SE stents. Disclosures J. Sambursky: None. A. Padalia: None. R. Gandhi: None. M. Bellew: None. F. Hellinger: None.

Background Endovascular thrombectomy RCTs used different imaging selection modalities and criteria. Early window (0–6 hours) trials mostly used simple CT, while DAWN and DEFUSE3 utilized advanced perfusion images (CTP/MRP) beyond 6 hours. Thus, optimal imaging selection criteria for thrombectomy is unknown. Method In this multicenter prospective cohort study, consecutive anterior-circulation large vessel occlusion patients up-to-24 hours from last-known-normal were enrolled in 9 centers (January/16–February/18). All patients received CT and CTP with mismatch determination using RAPID software. Treating physicians documented imaging selection modality prior to thrombectomy. Patients were divided based on selection modality into CT versus CTP groups. A blinded independent core-lab adjudicated imaging profiles defined a priori (Good CT=ASPECTS≥6, Good CTP=core vol 1.2). The primary outcome (90 day mRS=0–2) was compared between the CT and CTP groups and for different CT and CTP profiles. Results Of 445 patients enrolled, 341 received thrombectomy (figure 1). Median/IQR age=66/57–77, NIHSS=17/12–21, LSN-to-GP=3.8 hours/2.6–5.7 (range=1.2–17.6). 20% had ICA occlusions, 62% M1, and 18% M2. Selection modality was CT in 42% and CTP in 58%, with similar good outcome (CT=53.3% vs 54.3%=CTP, aOR=0.6,95% CI: 0.3 to 1.5, p=0.3, figure 2a). There was no interaction with time, early vs late window, p=0.1. 87% had good CT and 89.6% had good CTP with comparable good outcome (CT=55.7% vs CTP=57.3, aOR=2.2, 95% CI: 0.5 to 10.9, p=0.3, figure 2b). In early window, the good outcome rates were 54.9% for good CT and 58% for good CTP; for late window, they were 58.7% and 57.1%, respectively. There was no interaction with time (p=0.5). 16.8% would have been excluded from thrombectomy based on either CT or CTP only; 40.5% of them had good outcome. Of patients potentially excluded by CT but qualified by CTP, 50% had good outcomes with thrombectomy and 33% with medical management only. Similarly, of those excluded by CTP but treated by CT, 27.8% had good outcomes with and 0% without thrombectomy, respectively (table 1). Furthermore, discordant profiles patients (Good CT-Poor CTP and Poor CT-Good CTP) with good reperfusion (mTICI ≥2b) had higher good outcome rates, compared to mTICI Thrombectomy did not confer good outcomes in patients with Poor CT-Poor CTP. Conclusion Good outcome rates were comparable in patients selected for thrombectomy by CT versus CTP and those with good imaging profiles on either CT or CTP irrespective of the treatment time window, early or late. However, both imaging modalities excluded a similar number of patients who may benefit from the intervention. Our results will be validated in a randomized trial (SELECT2). Disclosures A. Sarraj: 1; C; Principal Investigator of the SELECT and SELECT 2 trials – unrestricted grant from Stryker Neurovascular to UT McGovern-Houston. 2; C; Consultant and Speaker for Stryker Neurovascular, Advisory Board – Stryker Neurovascular. 6; C; UT-Memorial Hermann Center PI for the Trevo Registry and DEFUSE 3 TRIAL, Steering Committee –ASSIST Registry. A. Hassan: None. R. Gupta: None. C. Sitton: None. J. Grotta: None. C. Cai: None. G. Cutter: None. B. Imam: None. S. Reddy: None. K. Parsha: None. N. Vora: None. M. Abraham: None. R. Edgell:None. F. Hellinger: None. D. Haussen: None. H. Kamal: None. L. McCullough: None. M. Lansberg: None. S. Savitz: None. G. Albers: None.

Background: Collateral circulation to the ischemic territory is a pivotal factor in outcomes after acute ischemic stroke. Extent of angiographic collaterals prior to endovascular therapy has been linked with reperfusion in previous trials, yet the mechanism remains unclear. We analyzed whether downstream collateral grade influences the pace and degree of ultimate reperfusion. Methods: The angiography dataset collated by the STRATIS Core Lab was analyzed to relate the grade of collateral circulation (ASITN) with adjudicated procedural time metrics to exact time of first TICI ≥ 2A and with the final eTICI score, delineating reperfusion into 7 distinct categories. Results: Collateral grade on routine angiography injections was available in 574/984 (58%) of STRATIS subjects (age 67.5 ± 15.1, 47% women, baseline NIHSS 16.8 ± 5.5). Collaterals included 203/574 (35.4%) with ASITN 3-4, 291/574 (50.7%) ASITN 2 and 80/574 (13.9%) ASITN 0-1. TICI ≥ 2A was achieved at 32.4 ± 23.5 minutes from angiography start and 26.4 ± 18.6 minutes from visualization of the arterial occlusion. The eTICI included 78 TICI 3 (13.6%), 140 TICI 2C (24.4%), 226 TICI o2B (39.3%), 68 TICI m2B (11.8%), 44 TICI 2A (7.7%), 4 TICI 1 (0.7%) and 14 TICI 0 (2.4%). More robust collateral grade was strongly associated with lower NIHSS (15.9 ± 5.4 (ASITN 3-4); 16.7 ± 5.5 (ASITN 2); 19.6 ± 5.1 (ASITN 0-1); p Collaterals and reperfusion were linked at all occlusion sites (ICA, M1, M2, BA). Conclusions: Collaterals on routinely available angiography prior to thrombectomy in STRATIS were strikingly tied to both the speed and degree of final reperfusion, across every site of arterial occlusion.

Background: ASPECTS is routinely used to estimate ischemic lesion burden in acute stroke, yet the topography and influence of collaterals has been unexplored. Imaging selection for endovascular therapy in various time epochs may also be simplified with ASPECTS. We leveraged the large-scale registry data of STRATIS to discern the role of collaterals, time and other factors in ASPECTS topography at baseline. Methods: The STRATIS Imaging Core Lab, blind to all clinical data, independently determined ASPECTS scores and regional involvement in anterior circulation occlusions. Collateral status on baseline angiography was scored by ASITN grade. Statistical analyses described ASPECTS regional involvement or topography based on arterial occlusion site and other variables available prior to intervention, determining the influence of collaterals and time duration from onset to imaging. Results: Baseline ASPECTS (n=573) was median 8.0 (2, 10). ASPECTS regions involved were lenticular nuclei 62.3% (357/573), insula 42.2% (242/573), caudate 23.4% (134/573), M2 13.6% (78/573), M4 9.4% (54/573), M5 9.2% (53/573), M1 4.0% (23/573), M3 2.1% (12/573), M6 1.9% (11/573) and internal capsule 0.2% (1/573). Distinct patterns or topography differentiated ICA, M1 and M2 arterial occlusion sites at angiography. Overall, higher ASPECTS (7-10 vs. ≤ 6) was linked with more robust collaterals (p Conclusions: ASPECTS topography and the extent of ischemic changes are a product of arterial occlusion site, collateral status and time duration. ASPECTS may infer collateral status, a pivotal determinant of outcome in endovascular therapy, irrespective of time from symptom onset.

Background: Serial ASPECTS of ischemic stroke lesion evolution from baseline to 24-hours has been established as an effective surrogate endpoint in endovascular therapy. The use of this imaging shift has not been implemented beyond thrombectomy trials to estimate impact of endovascular therapy in large-scale registry data. Methods: The STRATIS Imaging Core Lab, blind to all clinical data, independently determined ASPECTS scores on baseline and 24-hour studies. ASPECTS regional involvement and resulting total scores were analyzed in anterior circulation occlusions in STRATIS. Statistical analyses calculated the proportion of subjects with 0 ASPECTS score shift and separately, those with shifts >4, 5, 6 points. Clinical predictors of ASPECTS shift and regional involvement were determined. Results: Baseline ASPECTS (n=517) was 8.2 ± 1.59 (median 8.0 (2, 10)) and 24-hour ASPECTS (n=547) was 6.0 ± 2.92 (median 7.0 (0, 10)). Serial ASPECTS (n=487) revealed change of -2.1 ± 2.41 (median-1.0 (-10, 3)). Absolutely no change in ASPECTS, or 0 shift from baseline to 24 hours, occurred in 157/487 (32%). Substantial ASPECTS decline of ≥4 occurred in 117/487 (24%), with ≥5 in 76/487 (16%) and ≥6 in 51/487 (10%). ASPECTS decline was linked with baseline collaterals (ASITN 4 (n=19; -0.9 ± 1.05); 3 (n=117; -0.8 ± 1.21); 2 (n=140; -2.6 ± 2.27); 1 (n=29; -3.6 ± 2.34); 0 (n=10; -4.2 ± 3.08)) and the degree of subsequent reperfusion (oTICI 3 (n=63; -1.1 ± 1.94); 2B (n=282; -1.9 ± 2.32); 2A (n=103; -3.4 ± 2.38); 1 (n=2; -3.0 ± 1.41); 0 (n=10; -4.0 ± 2.75)). Baseline predictors of ≥6 ASPECTS decline included previous TIA (OR 3.10 (95%CI 1.32, 7.31), diabetes (OR 2.23 (95%CI 1.22, 4.07)) and baseline NIHSS (OR 1.10 (95%CI 1.03, 1.16). Conclusions: Frozen ASPECTS or 0 shift from baseline to 24 hours occurs in about 1/3 of all cases treated with endovascular therapy in a large-scale registry. Poor collaterals, prior TIA, diabetes and elevated baseline NIHSS may be important predictors of those likely to experience infarct evolution despite reperfusion, identifying optimal candidates for neuroprotection with endovascular therapy.

Introduction/Purpose The Penumbra START Trial is a multicentre, prospective, single-arm trial with a primary aim of determining whether core infarct size on pre-treatment neuroimaging predicts clinical response to intra-arterial acute stroke therapy. Materials and Methods For this study, major inclusion criteria include presence of proximal artery occlusion in the anterior circulation, baseline NIHSS score of 10 or greater, evaluable pre-treatment neuroimaging [noncontrast CT (NCCT), CTA source imaging, CT perfusion or MRI DWI], and treatment with the Penumbra System within 8 hours. Core infarct size was evaluated by a blinded imaging Core Laboratory. As pre-specified, infarcts were trichotomised into small [ASPECTS 8–10 (NCCT, CTA-SI) or lesion volume 100 cc). In total, 146 patients were enrolled at 27 centres, including 104 patients with Core Lab review and evaluation at 90 days. Good clinical outcome is defined as mRS 0–2 at 90 days. Case review is still ongoing, and statistical analysis is from the 104 patients with complete information. We will update results at the time of the meeting. Results Mean age is 66 ± 14, including 56% females. Median baseline NIHSS score is 19 (IQR14–22), and 58% of patients had occlusions located on their left side. Overall, TIMI 2–3 revascularisation was achieved in 85%. Forty-eight patients had a good outcome at 90 days (46%); 28 patients died (27%). The number of evaluable scans for each imaging method was: 31 CTP, 82 CTA-SI, 79 NCCT, and 6 DWI. After pooling all modalities in an aggregate analysis, a statistically significant relationship was found between core infarct size and good outcome, such that worse outcomes were found only in the large infarct group. The rate of 90-day good outcome was 54% in small, 56% in medium, and 19% in large infarcts (p=0.0010), despite similar rates of recanalisation (79% small, 93% medium, 84% large). Independent predictors of good outcome were age, baseline NIHSS score, time from onset to recanalisation, and infarct volume. Thirteen patients experienced symptomatic ICH (13%). Conclusion Pre-treatment neuroimaging is important in identifying patients with large infarcts who are unlikely to respond to mechanical thrombectomy. These data support the use of rigorous imaging criteria in patient selection. Disclosures D. Frei: 3; C; Penumbra, Inc. A. Yoo: 1; C; Penumbra, Inc. D. Heck: None. F. Hellinger II: None. V. McCollom: None. D. Fiorella: None. A. Turk III: 3; C; Penumbra, Inc. T. Malisch: None. O. Zaidat: 1; C; Penumbra, Inc. 3; C; Penumbra, Inc. M. Alexander: None. Z. Chaudhry: None. R. Gonzalez: None. L. Barraza: 5; C; Penumbra, Inc. A. Bose: 4; C; Penumbra, Inc. 5; C; Penumbra, Inc. S. Sit: 5; C; Penumbra, Inc. 6; C; Penumbra, Inc.

Introduction/purpose There is no standard imaging approach for EVT patient selection. CT remains the most widely used modality for stroke evaluation. Ischemic change on non-contrast CT (NCCT) quantified using ASPECTS has been demonstrated to predict clinical response to EVT. To date, definitive studies evaluating the impact of CTA source image (CTA-SI) pre-treatment ASPECTS (pre-ASPECTS) on outcomes following EVT are lacking. START was a prospective, multicenter study to evaluate the influence of pre-treatment core infarct size in patients undergoing endovascular stroke therapy using the Penumbra System. Materials and Methods The imaging method was at each center9s discretion and included NCCT, CTA-SI, CT perfusion, or MRI diffusion imaging. This study focused on the preliminary CTA-SI results. Results are reported from an interim analysis of the START trial data as adjudicated by a central Core Laboratory. Graded in a blinded fashion, ASPECTS was analyzed according to the a priori classification (0–4, 5–7, 8–10), as well as using the entire scale. Clinical outcomes were dichotomized as 90-day modified Rankin Scale scores of 0–2 (good) vs 3–6. Univariate and multivariate analyses were performed to determine predictors of outcome. Results Of the 147 patients enrolled, 77 met study criteria for this interim analysis. The mean age was 66.0±14.1 years; median NIHSS was 19 (14–24). Target vessel occlusions were in the ICA (22.1%), MCA (75.3%), and other (2.6%). The median pre-ASPECTS on CTA-SI was 6 (4–7). There were 20 (26%) patients with scores of 0–4, 43 (55.8%) with 5–7, 14 (18.2%) with 8–10. The rate of TIMI 2–3 revascularization was 85.3% (64/75). The median time from groin puncture to aspiration discontinuation was 71.5 (40–108) min. 37 (48.1%) patients achieved a good 90-day outcome. 22 (28.6%) died. Four (5.2%) patients suffered from symptomatic hemorrhage, and 11 (14.3%) suffered from asymptomatic hemorrhage. Higher pre-ASPECTS on CTA-SI was significantly associated with good outcomes (median 6 (IQR 5–7) vs 5 (IQR 3–7), p 4 was the optimal threshold for identifying good outcomes (89% sensitivity, 38% specificity). Other univariate predictors of good outcome were lower age (p=0.01), lower NIHSS (p=0.04), revascularization time (p Conclusion Higher pre-treatment ASPECTS on CTA source images are associated with better outcomes following EVT. Comparative studies with NCCT ASPECTS are required to evaluate relative accuracy for patient selection. Competing interests D Frei: None. A Yoo: None. D Heck: None. F Hellinger II: None. V McCollom: None. D Fiorella: None. A Turk III: None. T Malisch: None. O Zaidat: None. M Alexander: None. T Devlin: None. E Levy: None. Q Shah: None. F Hui: None. M Goyal: None. B Ghodke: None. A Shaibani: None. M Harrigan: None. T Jovin: None. M Madison: None. Z Chaudhry: None. R Gonzalez: None. L Barraza: Penumbra, Inc. S Sit: Penumbra, Inc. A Bose: Penumbra, Inc.

ENEWED interest in cerebrovascular insufficiency has been brought about by a measure of success in the surgical t rea tment of certain forms of associated arteriosclerosis; however, relationships between cerebral ischenfia and demonstrable arterial pathology have not been elucidated by assessment of the functional s tatus of the circulation with available methods. Cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) so far reported in patients suffering from cerebrovascular insufficiency, utilizing the widely accepted inert-gas technique, have, in general, shown aberrations from normal only when hypotension was present or mentat ion was reduced. 1,2,s,lI Serial studies, using the Fick principle for determination of cerebral blood flow, carried out during therapeutic carotid ligation, detected a significant decrease in cerebral blood flow only when severe neurological deficit and altered state of consciousness resulted. 9 I t is not surprising tha t the information obtained may be limited in the

In Versuchen an Hunden mit kunstlicher Durchblutung wurden die Veranderungen der Kreislaufgrosen und des partiellen Sauerstoffdrucks (pO2) im arteriellen und venosen Blut sowie im zisternalen Liquor bei verschiedenen Perfusionsraten und Korpertemperaturen zwischen 37° und 10° C gemessen. Zur Messung des zisternalen O2-Gehalts wurde eine kleine Beckmannsche Platin-Mikroelektrode verwendet, die auf die verschiedenen angewandten Temperaturen geeicht war.

The circulation of the brain has been the object of more speculation and study than any other part of the body. All present methods of estimating cerebral blood flow, however, leave much to be desired. Since, for many practical purposes we are not interested in the blood flow per se but in whether or not the oxygenation of the brain is adequate, we have attempted to approach the problem of quantitative brain oxygen tension directly. The prime consideration was "what" to measure that might justifiably be called "mean tissue oxygen tension." As pointed out by Bronk et al. 1 and Bloor et al. 2 the spatial resolution of the oxygen electrode is such that the absolute value obtained from the cortex varies greatly with its position relative to blood vessels. Other obvious problems arise in using the exposed cortex, such as pulsation, movement, variations in electrode pressure, etc. However